All-electron product basis set: Application to plasmon anisotropy in simple metals

Abstract

An efficient basis set for products of all-electron wave functions is proposed, which comprises plane waves defined over the entire unit cell and orbitals confined to small non-overlapping spheres. The size of the set and the basis functions are, in principle, independent of the computational parameters of the band structure method. The approach is implemented in the extended LAPW method, and its properties and accuracy are discussed. The method is applied to analyze the dielectric response of the simple metals Al, Na, Li, K, Rb, and Cs with a focus on the origin of the anisotropy of the plasmon dispersion in Al and Na. The anisotropy is traced to tiny structures of the one-particle excitation spectra of Al and Na, and relevant experimental observations are explained. arXiv:1904.00968v1 [cond-mat.mtrl-sci] 1 Apr 2019

Impact of the energy dispersion anisotropy on the plasmonic structure in a two-dimensional electron system

“…Up to this point, we have analyzed systems having ideal band dispersions, where the Fermi surfaces are perfect regular polygons. However, even though the anisotropy of different symmetries has been measured in several materials, 25 the Fermi surface geometry differs from such an ideal shape. In order to establish whether our analysis realized for the ideal systems can also be valid in non-ideal realistic cases, here we study how the dielectric properties and the excitation spectra depend on the level of the anisotropy in a system with a four-fold band structure.…”

“…Thus, it was found that the in-plane anisotropy in the electronic structure leads to the anisotropic 2D plasmon dispersion in graphene, 10,19 borophene, 20,21 and black phosphorous. [22][23][24] Some previous works have analyzed the effect of anisotropy on the conventional 2D and 3D plasmons, [25][26][27] considering materials with an elliptical band dispersion, but no additional plasmon mode has been found there.…”

Full versus quasi-particle self consistency in vertex corrected GW approaches

“…Besides that, the appearance of two-point bosonic functions (such as polarizability P and screened interaction W) requires efficient basis set to represent them. For example, the so called product basis (PB) set [3][4][5] was designed specifically for this purpose. Greater complexity of GW approximation (as compared to DFT) unavoidably brings more differences in implementations which makes the reproducibility of results at the level of GW a more serious issue.…”